**********${requestScope.u.uname}

**********${sessionScope.u.uname}

${requestScope.a}

public class ModelAndView {

	/** View instance or view name String */
	private Object view;

	/** Model Map */
	private ModelMap model;

	/**
	 * Indicates whether or not this instance has been cleared with a call to {@link #clear()}.
	 */
	private boolean cleared = false;


	/**
	 * Default constructor for bean-style usage: populating bean
	 * properties instead of passing in constructor arguments.
	 * @see #setView(View)
	 * @see #setViewName(String)
	 */
	public ModelAndView() {
	}

	/**
	 * Convenient constructor when there is no model data to expose.
	 * Can also be used in conjunction with <code>addObject</code>.
	 * @param viewName name of the View to render, to be resolved
	 * by the DispatcherServlet's ViewResolver
	 * @see #addObject
	 */
	public ModelAndView(String viewName) {
		this.view = viewName;
	}

	/**
	 * Convenient constructor when there is no model data to expose.
	 * Can also be used in conjunction with <code>addObject</code>.
	 * @param view View object to render
	 * @see #addObject
	 */
	public ModelAndView(View view) {
		this.view = view;
	}

	/**
	 * Creates new ModelAndView given a view name and a model.
	 * @param viewName name of the View to render, to be resolved
	 * by the DispatcherServlet's ViewResolver
	 * @param model Map of model names (Strings) to model objects
	 * (Objects). Model entries may not be <code>null</code>, but the
	 * model Map may be <code>null</code> if there is no model data.
	 */
	public ModelAndView(String viewName, Map<String, ?> model) {
		this.view = viewName;
		if (model != null) {
			getModelMap().addAllAttributes(model);
		}
	}

	/**
	 * Creates new ModelAndView given a View object and a model.
	 * <emphasis>Note: the supplied model data is copied into the internal
	 * storage of this class. You should not consider to modify the supplied
	 * Map after supplying it to this class</emphasis>
	 * @param view View object to render
	 * @param model Map of model names (Strings) to model objects
	 * (Objects). Model entries may not be <code>null</code>, but the
	 * model Map may be <code>null</code> if there is no model data.
	 */
	public ModelAndView(View view, Map<String, ?> model) {
		this.view = view;
		if (model != null) {
			getModelMap().addAllAttributes(model);
		}
	}

	/**
	 * Convenient constructor to take a single model object.
	 * @param viewName name of the View to render, to be resolved
	 * by the DispatcherServlet's ViewResolver
	 * @param modelName name of the single entry in the model
	 * @param modelObject the single model object
	 */
	public ModelAndView(String viewName, String modelName, Object modelObject) {
		this.view = viewName;
		addObject(modelName, modelObject);
	}

	/**
	 * Convenient constructor to take a single model object.
	 * @param view View object to render
	 * @param modelName name of the single entry in the model
	 * @param modelObject the single model object
	 */
	public ModelAndView(View view, String modelName, Object modelObject) {
		this.view = view;
		addObject(modelName, modelObject);
	}


	/**
	 * Set a view name for this ModelAndView, to be resolved by the
	 * DispatcherServlet via a ViewResolver. Will override any
	 * pre-existing view name or View.
	 */
	public void setViewName(String viewName) {
		this.view = viewName;
	}

	/**
	 * Return the view name to be resolved by the DispatcherServlet
	 * via a ViewResolver, or <code>null</code> if we are using a View object.
	 */
	public String getViewName() {
		return (this.view instanceof String ? (String) this.view : null);
	}

	/**
	 * Set a View object for this ModelAndView. Will override any
	 * pre-existing view name or View.
	 */
	public void setView(View view) {
		this.view = view;
	}

	/**
	 * Return the View object, or <code>null</code> if we are using a view name
	 * to be resolved by the DispatcherServlet via a ViewResolver.
	 */
	public View getView() {
		return (this.view instanceof View ? (View) this.view : null);
	}

	/**
	 * Indicate whether or not this <code>ModelAndView</code> has a view, either
	 * as a view name or as a direct {@link View} instance.
	 */
	public boolean hasView() {
		return (this.view != null);
	}

	/**
	 * Return whether we use a view reference, i.e. <code>true</code>
	 * if the view has been specified via a name to be resolved by the
	 * DispatcherServlet via a ViewResolver.
	 */
	public boolean isReference() {
		return (this.view instanceof String);
	}

	/**
	 * Return the model map. May return <code>null</code>.
	 * Called by DispatcherServlet for evaluation of the model.
	 */
	protected Map<String, Object> getModelInternal() {
		return this.model;
	}

	/**
	 * Return the underlying <code>ModelMap</code> instance (never <code>null</code>).
	 */
	public ModelMap getModelMap() {
		if (this.model == null) {
			this.model = new ModelMap();
		}
		return this.model;
	}

	/**
	 * Return the model map. Never returns <code>null</code>.
	 * To be called by application code for modifying the model.
	 */
	public Map<String, Object> getModel() {
		return getModelMap();
	}


	/**
	 * Add an attribute to the model.
	 * @param attributeName name of the object to add to the model
	 * @param attributeValue object to add to the model (never <code>null</code>)
	 * @see ModelMap#addAttribute(String, Object)
	 * @see #getModelMap()
	 */
	public ModelAndView addObject(String attributeName, Object attributeValue) {
		getModelMap().addAttribute(attributeName, attributeValue);
		return this;
	}

	/**
	 * Add an attribute to the model using parameter name generation.
	 * @param attributeValue the object to add to the model (never <code>null</code>)
	 * @see ModelMap#addAttribute(Object)
	 * @see #getModelMap()
	 */
	public ModelAndView addObject(Object attributeValue) {
		getModelMap().addAttribute(attributeValue);
		return this;
	}

	/**
	 * Add all attributes contained in the provided Map to the model.
	 * @param modelMap a Map of attributeName -> attributeValue pairs
	 * @see ModelMap#addAllAttributes(Map)
	 * @see #getModelMap()
	 */
	public ModelAndView addAllObjects(Map<String, ?> modelMap) {
		getModelMap().addAllAttributes(modelMap);
		return this;
	}


	/**
	 * Clear the state of this ModelAndView object.
	 * The object will be empty afterwards.
	 * <p>Can be used to suppress rendering of a given ModelAndView object
	 * in the <code>postHandle</code> method of a HandlerInterceptor.
	 * @see #isEmpty()
	 * @see HandlerInterceptor#postHandle
	 */
	public void clear() {
		this.view = null;
		this.model = null;
		this.cleared = true;
	}

	/**
	 * Return whether this ModelAndView object is empty,
	 * i.e. whether it does not hold any view and does not contain a model.
	 */
	public boolean isEmpty() {
		return (this.view == null && CollectionUtils.isEmpty(this.model));
	}

	/**
	 * Return whether this ModelAndView object is empty as a result of a call to {@link #clear}
	 * i.e. whether it does not hold any view and does not contain a model.
	 * <p>Returns <code>false</code> if any additional state was added to the instance
	 * <strong>after</strong> the call to {@link #clear}.
	 * @see #clear()
	 */
	public boolean wasCleared() {
		return (this.cleared && isEmpty());
	}


	/**
	 * Return diagnostic information about this model and view.
	 */
	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder("ModelAndView: ");
		if (isReference()) {
			sb.append("reference to view with name '").append(this.view).append("'");
		}
		else {
			sb.append("materialized View is [").append(this.view).append(']');
		}
		sb.append("; model is ").append(this.model);
		return sb.toString();
	}
}

      ：
package com.sxt.web;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.multiaction.MultiActionController;

import com.sxt.po.User;

@Controller
@RequestMapping("/user.do")
public class UserController extends MultiActionController  {
	
	@RequestMapping(params="method=reg")
	public ModelAndView reg(String uname){
		ModelAndView mv = new ModelAndView();
		mv.setViewName("index");
//		mv.setView(new RedirectView("index"));
		
		User u = new User();
		u.setUname("  ");
		mv.addObject(u);   //     ，  ，      。    ”        ”。             。
		mv.addObject("a", "aaaa");
		return mv;
	}

}
<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
  </head>
  <body>
	   <h1>${requestScope.a}</h1>
	   <h1>${requestScope.user.uname}</h1>
  </body>
</html>
     ：http://localhost:8080/springmvc03/user.do?method=reg
   ：